The present invention relates to a silicone based coating composition for surface-releasing film of, more particularly, to a silicone-based coating composition capable of giving an antistatic surface-releasing plastic film having excellent adhesion of the coating layer to the substrate, transparency and surface releasability even by omitting an antistatic undercoating.
It is a well established technology to impart a plastic film with surface releasability by coating the film surface with an organopolysiloxane based coating composition. A serious problem in manufacturing and handling of such a coated film is that the strong electrostatic charging of the organopolysiloxane causes attraction and deposition of dusts on the coated surface and sticking of coated films to each other due to the static electricity.
Various attempts and proposals have been made to overcome this difficulty. For example, coating with an organopolysiloxane-based coating composition is preceded by an undercoating of the film surface with an antistatic undercoating agent such as a partial hydrolysis product of a silicate compound (see, for example, Japanese Patent Kokai No. 60-141533). It is also a conventional means to use a surface active agent as an antistatic coating agent or the organopolysiloxane-based coating composition is compounded with an antistatic resinous additive.
These prior art methods are disadvantageous in respect of the additional step in obtaining an antistatic surface-releasing silicone-based coating layer resulting in a decrease in the productivity and in an increase in the production costs. Pre-treatment of the plastic film with a surface active agent may sometimes cause inhibition of curing and decrease in the heat resistance of the organopolysiloxane so that lowering is unavoidable in the quality of the resulting surface-releasing plastic film.